Carabiners—D-shaped rings with spring-loaded clips that climbers use—have become more popular for everyday use, like clipping keys, water bottles, or even USB drives to your backpack or gear. The Cool Tools blog features an S-Biner, a modified carabiner that has dual clips so you can attach items on either side. The S-Biner will set you back 5 bucks, and is available at Amazon.